Michael Walzer offers nine thoughts about this. Here's one of them:
But some [troop] withdrawal[s] from Iraq will be necessary, because the Democrats are really committed to a stronger effort in Afghanistan, which means more troops going there. More [American] troops going there and more troops from Europe too – or so the Democrats hope – and this might be the place to say that no new American foreign policy will be successful or sustainable unless the administration finds European partners who are prepared, along with the United States, to take some degree of responsibility for the way the world goes. American multilateralism - Afghanistan is just an example - is going to require a lot of work from the other sides, probably a lot more work than our European allies may currently have in mind.The other eight are here.